This effort represents an attempt to
build a complete index of Open Source / Free GIS related software
projects. In addition to those
alphabetized here, many great projects are listed at the end and will be
integrated soon. And this will all move to a proper database. The
definition of GIS is kept loose to encompass a broad range of projects
which deal with spatial technology.

If you know of other efforts that should
be listed please tell me about them. More importantly if I have made any
errors in characterizing a project, let me know:
bglewis<at>gmail.com.

Descriptive text gathered from the
project site is in quotes. Almost all of these projects fit the
definition of Open Source Software as defined by the Open Source Initiative, and most of
them fit the stricter definition of Free Software as defined by the Free Software Foundation.

AVCE00 "AVCE00 is an Open Source (i.e.
Free!) ANSI-C library that makes Arc/Info (binary) Vector Coverages
appear as E00! It allows you to read and write binary coverages just as
if they were E00 files." [ License: ? ]

Batik "Batik is a Java(tm) technology
based toolkit for applications or applets that want to use images in the
Scalable Vector Graphics (SVG) format for various purposes, such as
viewing, generation or manipulation." [License: Apache
Batik ]

BBBike
"BBBike is an information system for cyclists in Berlin and Brandenburg
(Germany). The application has the following features: 1) Display a map
with streets, railways, rivers, parks, altitude and other features. 2)
Find and show routes between two points. The route-finder can be
customized to match the cyclists preferences (fastest or nicest route,
keep wind direction and hills into account etc.). 3) A bike power
calculator. 4) Automatically fetch current Berlin weather data." [ License: GNU
General Public License (GPL) ]

BuddySpace
"BuddySpace is an instant messenger with four novel twists: (1) it
allows optional maps for geographical & office-plan visualizations
in addition to standard 'buddy lists'; (2) it is built on open source
Jabber, which makes it interoperable with ICQ, MSN, Yahoo and others;
(3) it is implemented in Java, so it is cross-platform; (4) it is built
by a UK research lab, so it is 100% free with full sources readily
available. [ License: Academic
Free License (AFL), Jabber
License ]

Bundler"Bundler is a structure-from-motion
(SfM) system for unordered image collections (for instance, images from
the Internet) written in C and C++. Bundler takes a set of images, image
features, and image matches as input, and produces a 3D reconstruction
of camera and (sparse) scene geometry as output." [
License: ? ]

CartoDB
"CartoDB is an open source tool that allows for the storage and
visualization of geospatial data on the web. It was built to make it
easier for people to tell their stories by providing them with flexible
and intuitive ways to create maps and design geospatial applications."

Cartaro
"Cartaro is the web mapping platform that brings the power of the best
open source geospatial components into a content management system." [
License: ? ]

Census
Data Conversion "Dr.
Bruce Ralston has developed a number of software programs to make
extracting and mapping of Census data as easy and inexpensive as
possible. These programs are designed to work with a number of current
and legacy data products produced by the US Census and other agencies."
[License:?]

Cesium
"Cesium is a JavaScript library
for creating 3D globes and 2D maps in a web browser without a plugin. It
uses WebGL for hardware-accelerated graphics, and is cross-platform,
cross-browser, and tuned for dynamic-data visualization. [ License: Apache 2.0
]

Chameleon
"Chameleon technology represents a revolutionary advancement in Web
mapping technology. It has been developed by DM Solutions with the goal
of producing a highly customizable and adaptable environment for
deploying and managing Web mapping applications."
[ License: DM
Solutions License ]

CityTracking
"...CityTracking
is intended to be a public, open source project that takes data about
cities and lays it open for examining from many angles so it can be
optimized for use by city personnel, journalists, and the public
(including businesses). Along the way we’ll release server-side code
bases, mapping algorithms, managed datasets, APIs and API specs, and
new views on data." Software: https://github.com/Citytracking/[License:?]

D3.js
"a JavaScript library for manipulating documents based on data. D3
helps you bring data to life using HTML, SVG and CSS." [ License: ? ]

DCMMS "A web-based maintenance management
system for water and waste water networks. Allows to store customer
complaints and issue workorder sheets. Rather than using street names,
maps and landmarks are used for navigation." Uses PostGIS. [
License: GNU
General Public License (GPL) ]

Deegree"Deegree is open
source software for spatial data infrastructures and the geospatial
web. Deegree includes components for geospatial data management,
including data access, visualization, discovery and security."
[ License: GNU
Lesser General Public License (LGPL) ]

Demeter
Terrain Engine
"Demeter is a cross-platform C++ library that renders 3D terrains using
OpenGL. Demeter is designed for fast performance and good visual quality
and makes use of advanced techniques such as dynamic tessellation
(adaptive mesh) to render vast landscapes in real-time, without the need
for high-end hardware. It is written as a stand-alone component that can
be easily integrated into any kind of application." [
License: GNU
Lesser General Public License (LGPL) ]

dlgvu "dlgvu is an interactive Digital Line Graph (DLG) viewer for Unix,
written in the Icon programming language." [ License: Public Domain ]

DNRGPS Converts GPX, CSV, and KML files
to shape. "DNRGPS is an update to the popular DNRGarmin application.
DNRGPS and its predecessor were built to transfer data between Garmin
handheld GPS receivers and GIS software." [
License: ?]

EDBS "This page is about the german
topographic data transfer standard EDBS/ATKIS and a reader for this
format. Owing to the specific nature of this data format, the following
information is exclusively available in German." [
License: GNU
General Public License (GPL) ]

E-FOTO “This
project, called E-FOTO, aims to develop and manage an educational
photogrammetric softcopy kit. It is based on two main principles: the
total freedom of the software under development and the self-teaching
approach.” [ License: ?]

FlightGear"FlightGear
is an open-source flight simulator. It supports a variety of popular
platforms (Windows, Mac, Linux, etc.) and is developed by skilled
volunteers from around the world." [ License: GNU
General Public License (GPL) ]

FreeType
"Is written in C, designed to be
small, efficient, highly customizable, and portable while capable of
producing high-quality output (glyph images) of most vector and bitmap
font formats." [ License: FreeType
or GNU ]

FWTools
"FWTools is a set of Open Source GIS binaries for Windows (win32) and
Linux (x86) systems. It was previously known as OpenEV_FW. The kits are
intended to be easy for end users to install and get going with. No
fudzing with building from source, or having to collect lots of
interrelated packages. FWTools includes OpenEV, GDAL, MapServer, PROJ.4
and OGDI as well as some supporting components. [ License: Various Open
Source ]

GDAL/OGR"GDAL is a translator library for raster geospatial data formats
that is released under an Open Source license. As a library, it presents
a single abstract data model to the calling application for all
supported formats." [ License:
MIT]

Geocoder "This is the submission that won
the 2002 Google Programming Contest. It includes a geocoder (which uses
TIGER/Line data to turn street addresses into latitude/longitude
coordinates), a simple indexer that looks for addresses and keywords in
documents, and a query engine to search for documents matching certain
keywords that also contain addresses within a certain distance of a
target location." [ License: GPL
and Google ]

geocoder.us
"Geocoder.us is a public service providing free geocoding of addresses
and intersections in the United States. The geocoding service relies on
Geo::Coder::US, a Perl module available for download from the CPAN. [ License: GNU
General Public License (GPL) ]

GEODAS "GEODAS (GEOphysical DAata System) is an interactive database
management system developed by the National Geophysical Data Center
(NGDC) for use in the assimilation, storage and retrieval of geophysical
data." [ License: free for noncommercial use ]

GeoJasPer
"GeoJasPer is a free and open source Geo supporting command line
transcoder between JPEG2000 and other formats. i.e. Converts image data
from one format to another correctly transferring Geo information
between GeoTiff and GeoJp2™ (GeoJpeg2000). [ License: ? ]

GeoMajas
"Geomajas is an enterprise-ready open sourceGIS
framework for the web. It has client-server integration for displaying
and editing of geographic data. Geomajas has integrated security and is
endlessly scalable." [ License: GNU
General Public License (GPL) ]

Geometry
Utility Library "GUL is a library of C++ functions. It
mainly contains basic functions for tesselating and manipulating NURBS
curves and surfaces, as well as functions for interpolating and
approximating data points with NURBS curves and surfaces. It also
contains some functions related to Computational Geometry, like
triangulating general polygons, intersection of 2D polygons, kd-tree,
exact arithmetic and other useful stuff." [ License: ? ]

GeoNetwork
OpenSource "GeoNetwork
is a catalog application to manage spatially referenced resources. It
provides powerful metadata editing and search functions as well as an
embedded interactive web map viewer. It is currently used in numerous
Spatial Data Infrastructure initiatives across the world."
[ License: GNU
Lesser General Public License (LGPL) ]

GeOxygene
"A Spatial data GeOxygene aims at providing an open framework which
implements OGC/ISO
specifications for the development and deployment of geographic (GIS)
applications. It is a open source contribution of the COGIT
laboratory at the IGN (Institut
Géographique National), the French National Mapping Agency. GeOxygene is
based on Java and open source technologies and provides users with an
extensible object data model (geographic features, geometry, topology and
metadata) which implements OGC
specifications and ISO standards
in the geographic information domain. The support of the Java interfaces
developed by the open source GeoAPI
project is planned." [ License: GNU
Lesser General Public License (LGPL) ]

GeoRuby
"GeoRuby provides geometric data types from the OGC "Simple Features for
SQL" specification. A plugin for Rails which manages PostGIS geometric
columns in a transparent way is also provided. [ License: MIT ]

GEOS
"GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology
Suite (JTS). As such, it aims to contain the complete functionality of
JTS in C++. This includes all the OpenGIS "Simple Features for SQL"
spatial predicate functions and spatial operators, as well as specific
JTS topology functions." [ License: GNU
Lesser General Public License (LGPL) ]

GeoServer"GeoServer
is an open source software server written in Java that allows users to
share and edit geospatial data. Designed for interoperability, it
publishes data from any major spatial data source using open standards."
[ License: GNU General Public
License (GPL) ]

GeoToad
"GeoToad is a tool for
serious geocachers.
It lets you make advanced queries to find the perfect caches to hit on
your day out, and export them to any imaginable format." [
License: ? ]

GeoTools"GeoTools is an open source (LGPL)
Java code library which provides standards compliant methods for the
manipulation of geospatial data, for example to implement Geographic
Information Systems (GIS). The GeoTools library implements Open
Geospatial Consortium (OGC) specifications as they are developed."
[ License:
GNU General Public License (GPL) ]

GeoVista
Studio "GeoVISTA Studio is an open software development
environment designed for geospatial data. Studio is a programming-free
environment that allows users to quickly build applications for
geocomputation and geographic visualization." [
License: GNU
Lesser General Public License (LGPL) ]

GFC "GFC, or Geographic Foundation Class library,
is a set of C++ classes defining basic geographic data types, including
points, lines, rectangles, circles, polylines, rings, complex polygons,
rasters, and other atomic data types such as integer, real, varchar. GFC
also features abstractions of timestamps and time series which are
useful in capturing the dynamics of spatiotemporal data." [ License: ? ]

GIServer “GIServer
is a project based GeoTools. It is implementing functions as same as
ArcGIS Server (10) REST interface, developers with ArcGIS
Flex/JS/Silverlight API experience will have a free/open-source
ArcGIS-liked server to use.” [ License: ? ]

GIS Knoppix"GIS-Knoppix
is a bootable Linux CD with pre-installed GIS software.
It is based on Knoppix." [ License:
varies]

GISToolKit
"The GISToolkit software is an open source java toolkit for building
spatially enabled applications. It has some ability to read data from a
variety of data sources, and to display that information to the user." [
License: GNU
Lesser General Public License (LGPL) ]

GIMP"The
GIMP is the GNU Image Manipulation Program. It is a freely distributed
piece of software suitable for such tasks as photo retouching, image
composition and image authoring." [ License:
GNU General Public License (GPL) ]

GML4J "GML4J is a Java API for
facilitating work with the Geography Markup Language
(http://www.gmlcentral.com). GML is an XML-based framework for encoding
geography information adopted as a recommendation paper by OGC
(http://www.opengis.org)."
[ License: Apache Software License]

Gnuplot "Gnuplot
is a portable command-line driven graphing utility for Linux, OS/2, MS
Windows, OSX, VMS, and many other platforms. The source code is
copyrighted but freely distributed (i.e., you don't have to pay for it).
It was originally created to allow scientists and students to visualize
mathematical functions and data interactively, but has grown to support
many non-interactive uses such as web scripting." [
License:
GNU General Public License (GPL) ]

GPSBabel "GPSBabel
converts waypoints, tracks, and routes between popular GPS receivers and
mapping programs. It also has powerful manipulation tools for such
data." [ License: GNU General Public
License (GPL) ]

GPSMan "GPS Manager (GPSMan) is a graphical manager of GPS data that makes
possible the preparation, inspection and edition of GPS data in a
friendly environment. GPSMan supports communication and real-time
logging with both Garmin, Lowrance and Magellan receivers and accepts
real-time logging information in NMEA 0183 from any GPS receiver." [
License: GNU
General Public License (GPL) ]

GPSTk "The goal of the
GPSTk project is to provide an open source library and suite of
applications to the satellite navigation community--to free researchers
to focus on research, not lower level coding." [
License: GNU
General Public License (GPL) ]

GrADS "The Grid Analysis and Display System (Grads) is an interactive
desktop tool that is used for easy access, manipulation, and
visualization of earth science data. Grads has been implemented
worldwide on a variety of commonly used operating systems and is freely
distributed over the Internet." [ License: Grads
License ]

GSLIB "GSLIB is an acronym for Geostatistical Software LIBrary. This name
was originally used for a collection of geostatistical programs
developed at Stanford University over the last 15 years." [ License: ? ]

gvSIG
Desktop "gvSIG
is a Geographic Information System (GIS), that is, a desktop application
designed for capturing, storing, handling, analyzing and deploying any
kind of referenced geographic information..." [
License: GNU
General Public License (GPL) ]

HidroSIG
"HidroSIG is a
Geographical Information System (GIS) with special tools that will allow
one to make estimations and analysis of hydrological, climatic and
geomorphological variables. " [
License: GNU
Lesser General Public License (LGPL) ]

iGeoPortal
"iGeoPortal is the web-based portal framework of deegree. deegree is a
Java Framework offering the main building blocks for Spatial Data
Infrastructures (SDIs). Its entire architecture is developed using
standards of the Open Geospatial Consortium (OGC) and ISO Technical
Committee 211" [ License: GNU Lesser General
Public License (LGPL) ]

IRIT
IRIT is a solid modeling environment that allows one to model basic,
primitive based, models using Boolean operations as well as freeform
surface's based models. [License: ? ]

IVICS “IVICS was developed as a visualization tool
to facilitate selection of training samples from satellite images. It
has evolved into a general purpose visualization system which supports
several common satellite and remote sensing data formats.” [
License: GNU
General Public License (GPL) ]

ivtools "Ivtools is a suite of
free X Windows drawing editors for PostScript, TeX, and web graphics
production, as well as an embeddable and extendable vector graphic
shell." [License: ?]

jGridShift jGridShift is a small piece of
software for NTv2 transformation. It is written in Java and includes a
J2EE Connector Architecture (JCA) adapter. There is a sample GUI tool
and a sample web service. [
License: GNU
Lesser General Public License (LGPL) ]

JCS "The JCS Conflation Suite is an API
and set of interactive tools which perform conflation on spatial
datasets." [License:
?]

JUMP "The Java Unified Mapping Platform
(JUMP) is a GUI-based application for viewing and processing spatial
data. It includes many common spatial and GIS functions. It is also
designed to be a highly extensible framework for developing and running
custom spatial data processing applications." [License: ?]

KFLog "The
KFLog-Family is a suite of free OpenSource programs aimed at flight
planning and flight analysis for gliders. [License: ?]

KIDS
"The Key Indicator Data System (KIDS) has been developed by the World
Agriculture Information Centre (WAICENT) of the Food and Agriculture
Organization of the United Nations. KIDS is a software framework that
provides the ability to implement thematic information systems that
collect, reference, visualize, exchange and disseminate statistical,
survey and indicator data. KIDS was developed originally for the purpose
of collecting, mapping and disseminating food insecurity and
vulnerability indicators that are relevant to Food Insecurity and
Vulnerability Information and Mapping System (FIVIMS)." [License: ?]

Leaflet "Leaflet is a modern
open-source JavaScript library for mobile-friendly interactive maps.
Leaflet is designed with simplicity, performance and
usability in mind. It works efficiently across all major
desktop and mobile platforms out of the box, taking advantage of HTML5
and CSS3 on modern browsers while still being accessible on older ones."
[License: ?]

Libgeotiff
"Libgeotiff is a public domain library normally hosted on top of libtiff
for reading, and writing GeoTIFF information tags." [License: Public
Domain ]

libGRASS “The
libgrass package consists of the majority of the GRASS libgis, and
libdatetime library build as a standalone shared library suitable for
use by non-GRASS applications wishing to read and write GRASS databases.
Some additional functions have been added to simplify library
initialization and data access by non-GRASS applications.” [ License: MIT
]

Libvm
http://code.google.com/p/libmv/ "libmv is a structure from motion
library, which plans to one day take raw video footage or photographs,
and produce full camera calibration information and dense 3D models." [ License: MIT
]

libtiff "The library,
along with associated tool programs, should handle most of your needs
for reading and writing TIFF images on 32- and 64-bit machines. This
software can also be used on older 16-bit systems though it may require
some effort and you may need to leave out some of the compression
support. " [ License: Libtiff
License ]

*LightRod "...the
need arose for an open source geographic search engine, or proximity
search...the software is scalable to any number of records, and uses
'peano codes', or space filling curves to find the nearest results, no
matter what distance they are from the request." [License: ?]

Lx-Viewer"LX-Viewer
is a program that will allow you to open, view, print and convert
DWG or DXF files, typically used in
AutoCAD related technical drafting.”
[ License: modified version of the GPL ]

Majas
"MAJAS is a component framework for building rich Internet applications
(RIA) with sophisticated capabilities for the display, analysis and
management of geographic information." [ License: GNU
General Public License, Version 2 ]

MapBox"MapBox Streets is a highly accurate worldwide map powered by
up-to-the-minute data from the OpenStreetMap project. It's built to be
customized: change the map colors, show and hide features, and even
configure the labeling language to make it yours." [License: ?]

Mapwarper
"Mapwarper is an open source map geo-rectification, warping and
georeferencing application. It enables a user to upload an image, a
scanned map or aerial photo for example, and by placing control points
on a reference map and the image, to warp it, to stretch it to fit." [
License: ? ]

MapWindow "The
MapWindow GIS project includes a free and open source desktop geographic
information system (GIS) with an extensible plugin architecture; a GIS
ActiveX control; and C# GIS programmer library called DotSpatial."
[License: Mozilla
Public Licence 1.1]

MB-System "MB-System
is an open source software package for the processing and display of
bathymetry and backscatter imagery data derived from multibeam,
interferometry, and sidescan sonars." [ License: ? ]

*Mesa
"Mesa is an open-source
implementation of the OpenGL
specification - a system for rendering interactive 3D graphics. " [
License: ? ]

MetaPost
"MetaPost is a powerful language
for producing figures for documents to be printed on PostScript
printers, either directly or embedded in (La)TeX documents." [ License:
Public Domain ]

mezoGIS "mezoGIS is a GIS application, a
graphical interface to query and analyse spatial data. mezoGIS does not
store or compute data directly, but operates external PostGIS
databases."[
License: GNU
General Public License (GPL) ]

modestMaps
"Modest Maps is a small, extensible, and free
library for designers and developers who want to use interactive maps in
their own projects. It provides a core set of features in a tight, clean
package with plenty of hooks for additional functionality." [
License: ? ]

NRDB "NRDB
is a free database and mapping application for developing and
distributing environmental databases. It was designed to provide people
in developing countries with a powerful yet simple tool to assist in the
managing of their own resources. " [
License: GNU
General Public License (GPL) ]

Nunaliit
"The Nunaliit Atlas Framework aims to make
it easy to tell stories and highlight relationships between many
different forms of information from a variety of sources, using maps as
a central way to connect and interact with the data." [ License: New BSD
License ]

OGDI “OGDI
is the Open Geographic Datastore Interface. OGDI is an application
programming interface (API) that uses a standardized access methods to
work in conjunction with GIS software packages (the application) and
various geospatial data products. ” [
License: MIT
]

OGLE "OGLE
(OpenGLExtractor) is software package by Eyebeam R&D that allows for
the capture and re-use of 3D geometry data from 3D graphics applications
on Microsoft Windows." [
License: GNU
General Public License (GPL) ]

Open
3D GIS "A Open Source project with the main
goal to make a simple way to display 3D objects from a Geodatabase
(PostgreSQL/PostGIS) on the Web." [
License: ? ]

Open
CASCADE "Open CASCADE
Technology is a software development platform freely available in open
source. It includes C++ components for 3D surface and solid modeling,
visualization, data exchange and rapid application development." [
License: OpenCascade
]

OpenDMTP "The "Open Device Monitoring and
Tracking Protocol", otherwise known as OpenDMTP™, is a protocol and
framework that allows bi-directional data communications between servers
and devices (clients) over the Internet and similar networks. OpenDMTP
is particularly geared towards Location-based information (LBS) such as
GPS, as well as temperature and other data collected in
remote-monitoring devices. OpenDMTP is small, and is especially suited
for micro-devices such as PDA's, mobile phones, and custom OEM devices."
[License: Apache
Software License, version 2 ]

OpenLayers "OpenLayers makes it easy to put a
dynamic map in any web page. It can display map tiles and markers loaded
from any source." [ License: ? ]

OpenMap "BBN Technologies' OpenMap package is a JavaBeans based
programmer's toolkit. Using OpenMap, you can quickly build applications
and applets that access data from legacy databases and applications.
OpenMap provides the means to allow users to see and manipulate
geospatial information." [ License: OpenMap
License ]

osm2pgsql
"osm2pgsql is a command-line based program that converts OpenStreetMap
data to postGIS-enabled PostgreSQL databases." [ License: ? ]

Paradise
"The objective of the Paradise project is to design, implement, and
evaluate a scalable, parallel geographic information system that is
capable of storing and manipulating massive data sets." [ License: ? ]

Piccolo2D "A revolutionary way to create robust,
full-featured graphical applications in Java and C#, with striking
visual effects such as zooming, animation and multiple
representations." [ Mozilla
Public License ]

p.mapper
"The p.mapper framework is intended to offer broad functionality and
multiple configurations in order to facilitate the setup of a MapServer
application based on PHP/MapScript." [
License: MapServer
License ]

PolyMaps
"Polymaps is a free JavaScript library for making dynamic, interactive
maps in modern web browsers." [ License: ? ]

PROJ.4 The PROJ.4 cartographic projections library is used in many mapping
applications. [ License: MIT
]

PyCSW
"pycsw is an open source OGC CSW implementation written in Python." [ License: MIT
]

PySAL
"PySAL provides a suite of spatial analytical methods that developers
can incorporate into their own application development, and that spatial
analysts may customize to further their research." [ License: ? ]

Risiko "Risiko is a web based
tool that models impacts of different hazard events on population or
infrastructure. It is part of a set of Open Source Software tools called
Risk in a Box." [ License: ? ]

Shareabouts
"Shareabouts is a mapping tool to gather crowdsourced public input,
including suggested locations and comments." [License:
? ]

SharpMap "SharpMap
is an easy-to-use mapping library for use in web and desktop
applications. It provides access to many types of GIS data, enables
spatial querying of that data, and renders beautiful maps." [
License: GNU
Lesser General Public License (LGPL) ]

TerraLib "TerraLib is a GIS
classes and functions library, available from the Internet as open
source, allowing a collaborative environment and its use for the
development of multiple GIS tools." [
License: GNU
Lesser General Public License (LGPL) ]

TileStache
"TileStache is a Python-based server application that can serve up map
tiles based on rendered geographic data. You might be familiar with TileCache, the venerable open source
WMS server from MetaCarta. TileStache is similar, but we hope simpler
and better-suited to the needs of designers and cartographers." [
License: ? ]

Vis5d "Vis5d+ is intended as a
central repository for enhanced versions and development work on Vis5d,
a free OpenGL-based volumetric visualization program for scientific
datasets in 3+ dimensions. " [ License: GNU
General Public License (GPL) ]

Virtual
Terrain Project (VTP) "The goal of VTP is to foster
the creation of tools for easily constructing any part of the real world
in interactive, 3D digital form. This goal will require a synergetic
convergence of the fields of CAD, GIs, visual simulation, surveying and
remote sensing. VTP gathers information and tracks progress in areas
such as procedural scene construction, feature extraction, and rendering
algorithms." [ License: Public Domain ]

Walking
Papers "Print maps, draw on them, scan them back in and help
OpenStreetMap improve its coverage of local points of interests and
street detail." [ License:? ]

worldKit "worldKit is an easy to use and
flexible mapping application for the Web. Light weight GIS. It's a SWF
based app, configured by XML, data fed by RSS. Stand-alone use or
integration in larger projects." [
License: GNU
General Public License (GPL) ]

WorldMap
"The WorldMap platform is being developed by the Center for Geographic
Analysis (CGA) at Harvard to lower barriers for scholars who wish to
explore, visualize, edit, collaborate with, and publish geospatial
information. The system attempts to fill the niche between powerful
desktop-bound mapping applications, and lightweight web map solutions
with limited capacity." [ License: GNU
General Public License (GPL) ]

World
WindWorld Wind is a free, open source
API for a virtual globe. Written in Java so as to be cross-platform and
easy-to-use, World Wind allows developers to quickly and easily create
interactive visualizations of 3D globe, map and geographical
information." [ License:? ]

Xastir "Automatic
Packet Reporting System (APRS™) (also known as "Automatic Position
Reporting System") is an amateur radio based digital communication
system for real-time exchange of digital information to users on the
network. " [ License: GNU General Public
License (GPL) ]

XCSoar
"XCSoar is a tactical
glide computer originally developed for the Pocket PC platform. In 2005,
the originally commercial software was given to the open-source
community for further development and has constantly been improved
since. It is now a multi-platform application that currently runs on
Windows, Windows Mobile, Unix and even Android devices. " [
License: GNU
General Public License (GPL) ]

Xearth
"Xearth for Windows is a port of Kirk Johnson's original xearth program
to Microsoft Windows. Xearth renders a shaded image of the earth on your
desktop, as seen from your favorite vantage point in space." [ License:
? ]

Xplanet
"Xplanet was inspired by Xearth,
which renders an image of the earth into the X root window. All of the
major planets and most satellites can be drawn, similar to the Solar
System Simulator. A number of different map projections are also
supported, including azimuthal, Lambert, Mercator, Mollweide,
orthographic, and rectangular." [ License: GNU
General Public License (GPL) ]